1. Field of the Invention
The invention is based on an optical waveguide arrangement for a high-voltage insulator according to the introductory clause of claim 1.
2. Discussion of Background
A conventional optical waveguide arrangement for a high-voltage insulator is known from DE-A1-No. 34 26 536. There optical waveguides are attached, mechanically protected, in a straight line and uncoiled, to a cylindrical support element having a surface of limited electrical conductivity. The support element is permanently arranged at an insulator column filled with an insulating agent. The optical waveguides are conducted hermetically sealed through the insulator column. A coiling of the optical waveguide is considered to be disadvantageous in this case for mechanical and transmission reasons.
Optical waveguide arrangement for a highvoltage insulator, in which arrangement the voltage gradient along the optical waveguide between the high-voltage side and the ground potential side of the high-voltage insulator is reduced.
An advantage of the invention consists in the fact that the electric strength of the optical waveguide, which is normally relatively low in comparison with that of the high-voltage insulator, is compensated by the greater length of the optical waveguide. If glass fibers are used for the optical waveguides, transmission losses on the transmission path through the high-voltage insulator are negligible.
By providing a relative long surface leakage path i.e., 5 times greater than the height of the insulator, the voltage gradient is reduced to a greater extent.
In a preferred embodiment, the optical waveguide is wound at a steep pitch around an insulating coil located in the hollow space of the insulator. An advantage of the coil in the embodiment consists in the fact that its end terminations can fulfil several functions. In the upper termination or sealing end, an optical waveguide, which is of sufficient length for the high-voltage-conducting assembly, with optical waveguide connector can be accommodated. In the lower termination or terminal box, couplings for the fibre-optic output of the high-voltage-conducting assembly can be attached.
Alternatively, the optical waveguide can be arranged in a recess of groove in the coil or in a hollow coil to ensure good and positionally stable guidance of the optical waveguide.
If a flexible tube is used as coil, the possibility exists of drawing a universal optical waveguide to the required coil length. When the high-voltage insulator is ventilated, a self-supporting coil without vertical supports has the advantage of greater flashover strength.
Further, the optical waveguide can be embedded in the insulator tube which provides the advantage that his is done during the production of the insulator tube so that the optical waveguide is spirally conducted from one end to the other end of the insulator tube in one of the upper layers of the insulator tube.
In another implementation, the optical waveguide is embedded in an additional silicon layer on the insulator tube, which has the advantage that the bearing cross-section of the insulator tube is not reduced.
Advantageously, the silicon layer is provided with an optical waveguide recess in which that the optical waveguide can be subsequently inserted.
Providing the optical waveguide recess on the underside of the silicon shield enables the optical waveguide to be simply pressed in, which has a self-holding effect after completion of the high-voltage insulator.
The developments of the invention in which the optical waveguide is embedded in the insulator tube or in the above-noted silicon layer to have the common advantage that the optical waveguide does not come into contact with the medium (oil, sulfur hexafluoride SF.sub.6, foam) present in the interior of the high-voltage insulator. The axial voltage stress can be controlled by the pitch of the winding spiral. There are no optical waveguide related transitions in the interior space of the high-voltage insulator which could create sealing problems. There is also the common advantage that the optical waveguide is protected against external influences such as moisture and mechanical damage by the fibre-glassreinforced plastic and silicon layer.